933.    FINZEL, T. G.  Pyrophoric Iron.  I.  Preparation and Properties.  Jour. Am. Chem. Soc., vol. 52, 1930, pp. 142-149; Chem. Abs., vol. 24, 1930, p. 1275.

      Pyrophoric Fe can best be prepared by the reduction of Fe2O3 in H2 at 500 for 3 hr.  The Fe2O3 was precipitated from Fe (NO3)3 solutions of different concentrations to produce oxides of different degrees of dispersion, which, in turn, would influence the pyrophoric activity of the reduced Fe.  The pyrophoric Fe was inactivated by heating in H2, N2, or He.  Oxides of the highest degree of dispersion yield pyrophoric Fe most easily inactivated the ease of inactivation depending upon the degree of dispersion.  The time factor of inactivation for the different gases varied in the order:  He>N2>H2.  Inactivation is accompanied by a decrease in total surface.  Samples were produced that displayed pyrophoric activity at 78 and in air that had been thoroughly dried.